Liliya Yossifova

Antitumor activity of quaternized chitosan-based electrospun implants against Graffi myeloid tumor

Nanofibrous implants containing quaternized chitosan (QCh), poly(L-lactide-co-D,L-lactide) (coPLA), and the antitumor drug doxorubicin (DOX) were fabricated by electrospinning. The surface chemical composition and the morphology of the implants were characterized by XPS and SEM. In vitro cell viability studies demonstrated that QCh- and DOX-based implants exhibited high cytotoxicity against Graffi tumor cells. The implants efficiently inhibited the growth of Graffi tumor in hamsters with minimum weight loss. Insertion of QCh/coPLA/DOX implants in the place of removed tumor led to an increase in the animal survival rate and to a decrease in the percentage of recurrences.

Biological activities of selected polyphenol-rich fruits related to immunity and gastrointestinal health

Small fruits are a rich source of bioactive substances, including polyphenols, and are therefore suitable raw materials for the production of functional foods. In the current work, we studied the antioxidative properties of six fruits: rosehip, chokeberry, hawthorn, blackcurrant, blueberry and rowanberry via different methods (ORAC, TRAP, HORAC and inhibition of lipid peroxidation). Their effect on the production of reactive oxygen species (ROS) by phagocytes, antimicrobial properties against 11 human pathogens, and mitogenic effect on hamster spleen lymphocytes were also tested. Rosehip extract showed the highest antioxidant activity via ORAC, TRAP and HORAC assays, whereas blueberry extract was the most potent inhibitor of lipid peroxidation. All extracts inhibited ROS production of opsonized zymosan-activated phagocytes, indicating that extracts interfere with the signaling cascade of phagocyte activation upstream to the protein kinase C activation. Chokeberry, blackcurrant and rowanberry extracts revealed strong antimicrobial properties against a broad spectrum of microorganisms and also had the highest mitogenic activity.

Antitumor Activity of Glycosylated Molluscan Hemocyanins via Guerin Ascites Tumor

As observed in most molluscan hemocyanins, high-mannose type glycans were identified in hemocyanins from Rapana venosa (RvH), Helix lucorum (HlH) and keyhole limpet (Megatura crenulata). In addition, a glycan with a branching structure containing xylose, fucose and terminal methyl hexose was identified in β-HlH. We have examined the immuno-adjuvant properties of hemocyanins, their derivatives and conjugates associated with the cell mediated immunity in experimental tumor-bearing animals with ascites tumor of Guerin. After immunization of the animals with the experimental vaccine preparations, the highest values of splenic lymphocytes were observed in groups immunized with the conjugates RvH-TAg, β-HlH-TAg and KLH-TAg (42.3%; 40.8% and 40.58%, respectively) than with the native hemocyanins (36.5%; 35.1% and 32.4%, respectively). The immunization of rats with the hemocyanins β-HlH, RvH and KLH and their conjugates, prolonged the median survival time of tumor-bearing animals compared with non-immunized animals (39, 33, 31 and 7 days, respectively). Both hemocyanins β-HlH and RvH activate the immune system of the experimental animals and therefore could be a good alternative for KLH. For this reason they could be included into the composition of non-specific anti-tumor vaccines to enhance their effectiveness.

Quaternized chitosan-coated nanofibrous materials containing gossypol: preparation by electrospinning, characterization and antiproliferative activity towards HeLa cells.

Nanofibrous polylactide-based materials loaded with a natural polyphenolic compound gossypol (GOS) with antitumor properties were prepared by electrospinning. The nanofibrous materials were coated with a thin film of crosslinked quaternized chitosan (QCh). GOS incorporated in the nanofibrous mats was in the amorphous state. GOS release was diffusion-controlled and its in vitro release profiles depended on the mat composition. The nanofibrous materials exhibited high cytotoxicity towards HeLa tumor cells. Interestingly, it was particularly pronounced in the case of fibrous materials, which contain both QCh and GOS. The observed strong antiproliferative effect of the nanofibrous mats was mainly due to induction of cell apoptosis.

Antitumor activity of C-phycocyanin from Arthronema africanum (Cyanophyceae)

ABSTRACT Pure C-phycocyanin (C-PC) was isolated from Arthronema africanum to evaluate its potential antitumor effects in vivo and in vitro. Experimental myeloid Graffi tumor in hamsters was used as a model. The cell proliferation assay showed that C-PC treatment, at concentration of 100 µg mL -1 for 24 h, significantly inhibited the growth of Graffi tumor cells (51.4% viability). Agarose gel electrophoresis of the genomic DNA of treated cells displayed time- and concentration-dependent fragmentation pattern, typical for apoptosis. Apoptotic process was related to the increase in cellular manganese and copper/zinc superoxide dismutases and glutathione reductase activities, coupled with a low catalase activity. In vivo C-PC administration (5.0 mg kg -1 body weight) suppressed the tumor transplantability and growth, while the mean survival time of the tumor-bearing hamsters was increased. The results revealed promising antitumor activities of A. africanum C-PC and suggested the potential of this natural biliprotein pigment for future pharmacological and medical applications. The study provided new data on the mechanism of the C-PC-induced apoptosis in which the imbalance of antioxidant enzymes that favoured hydrogen peroxide accumulation might play a leading role. Key words: Antitumor activity, Arthronema africanum , In vivo , In vitro , C-pycocyanin, Myeloid Graffi tumor

Immunological Research on the Protective Properties of a Conjugate of Total Larval Antigen with Hemocyanin Derived from Helix Vulgaris Against Infection with Trichinella Spiralis

ABSTRACT Investigations suggest that resistance against Trichinella spiralis infection can be modified by application of a separate vaccine preparation, in this case—conjugated total antigen from Trichinella spiralis larvae with hemocyanin from Helix vulgaris. These effects are generally to reduce resistance at the level of the gut, and enhance it against the systemic phase of the infection. The mechanism, which induces these alterations is still not completely clear. Our results showed reduced tissue penetration of the nematode worms in muscles. In addition we have observed solid protective humoral and cellular immune response.

Cytotoxic and Apoptogenic Potential of Red Microalgal Polysaccharides

ABSTRACT The efforts of scientists are aimed at finding anti-cancer agents of natural origin which have high biological activity, low toxicity and broad spectrum of therapeutic activity. This study was designed to determine the cytotoxic properties of polysaccharides derived from the red microalgae Dixoniella grisea and Porphyridium cruentum and to elucidate the mechanism of their action on two permanent human cell lines MCF-7 (breast adenocarcinoma) and HeLa (cervical carcinoma), as well as on primary culture from Graffi myeloid tumor in hamsters. Our investigations indicated that both algal polysaccharides showed high cytotoxic and apoptogenic activities on cancer cells and may be a promising alternative to synthetic substances.

Highly Preferential Linker Histone Binding to Actinomycin D-Treated DNA

ABSTRACT Electromobility-shift assay (EMSA) was applied for studying the competition between the anticancer antibiotic actinomycin D (ACTD) and linker histones H1 and H5 for binding to DNA. ACTD is widely used in the treatment of some malignancies. Its binding to DNA occurs in two steps: initial intercalation between guanine and cytosine bases followed by invading the minor groove of the polynucleotide chain. As a consequence of this structural perturbation of DNA, a strong interference with the binding of important regulatory and functional proteins to DNA may occur. Here we present our recent experimental data obtained in a drug-competition assay between ACTD and linker histones H1 and H5 under the following conditions: i) simultaneous incubation of DNA with the antibiotic and histone; ii) preincubation of DNA with ACTD and subsequent addition of the histone; and iii) preincubation of DNA with histone and subsequent addition of the drug. Surprisingly, linker histones bound more effectively to ACTD-pretreated DNA than to the untreated control. The results obtained with plasmid DNA were confirmed using a series of various native and synthetic DNA fragments bearing different number of antibiotic targets. The same results were obtained with the globular domain of H5, the portion of the linker histone suggested to be most responsible for DNA binding. The data with another nuclear protein with similar DNA-binding properties as linker histones—HMGB1—showed strongly reduced contacts with ACTD-treated DNA compared with the untreated.